1. Field of the Invention
This invention relates to wheelchairs, and more particularly to independent access to wheelchairs from ground level as well as wheelchairs with adjustable seat heights.
2. Description of the Related Art
Wheelchair users today can accomplish incredible feats, such as participating in marathons, skiing, sky diving, scuba diving, etc. Normally, wheelchairs do not stop their occupants from living full and rich lives. Yet, one major problem faced by individuals in wheelchairs occurs when the wheelchair tips and ejects its occupant. This often occurs when the user reaches and leans too far forward or to one side. It may also occur outdoors on uneven terrain or when encountering all sorts of natural objects or obstacles, or even when attempting to transfer from the wheelchair to a bed or other location. Unless the individual has great upper body strength, he or she cannot climb back into the wheelchair independently, and sometimes must wait for long periods of time before help arrives. This situation can lead to potentially serious consequences.
None of the prior art addresses the need for getting back into the wheelchair should a mishap occur. Moreover, none of the prior art addresses the situation where the wheelchair user desires to be lowered from the normal operating height to the floor or ground. None of the wheelchairs in the prior art is capable of permitting the wheelchair user to safely lower himself or herself to the ground without tipping the chair and falling or using some type of assistance. Although some wheelchairs have been produced for pediatric applications or highly specialized situations that allow an individual to be lowered to the floor, the manufacturer limits their use to occupants no heavier than 80 lbs. Furthermore, they tend to be very large and bulky, cannot be used on a regular basis, and cannot be maneuvered in tight situations.
Another challenge for the wheelchair user is that it is difficult to reach objects higher than arm""s reach due to the restricted wheelchair seat height. Even if one employs a device such as a reacher, the lack of fine dexterity and tactile feedback is a problem. Moreover, the problems associated with a physically disabled person transferring to or from a wheelchair have long been recognized. The difficulty a physically challenged person has in moving from a wheelchair to another location, such as the passenger seat of a vehicle, is augmented by the differences in seat heights of the wheelchair and passenger seat or other support. In an attempt to overcome the problems associated with differences in seat heights, several solutions have been proposed.
U.S. Pat. No. 5,669,620 issued to Robbins discloses a laterally and vertically movable wheelchair seat for allowing a patient or physically challenged individual to be transported from the wheelchair to a fixed seat frame. The lateral and vertical movement is achieved by a jack mechanism which supports the seat, and is powered by a hand crank or electric motor, which raises the seat from a normal operating height.
U.S. Pat. No. 5,060,960 issued to Branscumb, et al. discloses a wheelchair comprising a foot-actuated hydraulic pump, similar to a barber""s chair, below the seat panel which allows an attendant to raise the seat to the desired level from a normal operating height.
U.S. Pat. No. 5,520,403 issued to Bergstrom, et al., discloses a wheelchair which allows a patient to be laterally transferred from the wheelchair to a desired location, such as a bed. The seat is a belt-like structure that laterally transports the user via a manual crank and may be adjusted upwardly from a normal operating height by turning a crank lead screw. The arms of the wheelchair articulate rearward and a transfer board extends from the seat to the bed for ease and safety of transportation.
These and other problems associated with the prior art are overcome by the provision of a wheelchair having a seat that can be adjusted between ground level and a normal wheelchair operating height, and between a normal operating height and an upper level above the normal operating height.
According to the invention, a wheelchair has a supporting frame with opposite sides, two or more wheels attached to the frame, and a seat operationally connected via adjusting means to the supporting frame between the opposite sides. The adjusting means are connected between the seat and supporting frame for adjusting the height of the seat relative to the supporting frame. This adjustment can range from a normal operating height associated with normal wheelchair operation and ground level to an upper level above the normal operating height. In this manner, a wheelchair occupant can be raised anywhere from the ground level to the normal operating height to the upper level by manipulation of the adjusting means. It should be noted that the wheelchair user may perform this manipulation independently and while in the wheelchair.
In one embodiment, the adjusting means comprises an elongate shaft connected to the seat for rotation about its longitudinal axis. At least one suspension cable has a first end connected to the supporting frame and a second end connected to the elongate shaft. Rotation of the shaft about its longitudinal axis in one direction causes the cable to wind around the shaft to thereby raise the seat, while rotation of the shaft in the opposite direction causes the cable to unwind from the shaft to thereby lower the seat.
Preferably, a first pair of cables have first ends connected to the opposite sides of the supporting frame at a forward portion thereof, and a second pair of cables have first ends connected to the opposite sides of the supporting frame at a rearward portion thereof. The second ends of the cables are preferably connected to opposite ends of the elongate shaft.
A torque arm can be telescopically or releasably connected to the shaft for rotating the shaft about its longitudinal axis in a power stroke direction. Preferably, a switch assembly is operatively connected to the shaft and seat. The switch assembly is movable to a first position that permits rotation of the shaft in the power stroke direction for winding the cables on the shaft and prevents rotation of the shaft in a direction opposite the power stroke direction to thereby prevent unwinding of the cable from the shaft. The switch assembly can also be moved to a second position for permitting free rotation of the shaft in the opposite direction for unwinding the cable from the shaft to thereby lowering or raising the seat relative to the neutral regular operational position.
A ratcheting mechanism can also be provided that is operatively connected between the shaft and torque arm for locking the shaft with the torque arm in the power stroke direction and permitting rotation of the torque arm with respect to the shaft when the torque arm is rotated in a recovery direction opposite the power stroke direction. During the power stroke with the switch assembly in the first position, the shaft is locked to the torque arm for rotation therewith and the shaft is unlocked from the seat. Likewise, the torque arm is unlocked from the shaft and the shaft is locked against rotation to the seat during the recovery stroke. In this manner, the seat can be ratcheted upward toward the normal seat height and locked against downward movement during the torque arm recovery stroke.
According to a further embodiment of the invention, the supporting frame includes a lower frame portion and an upper frame portion that is adjustable in height with respect to the lower frame portion. The seat is connected to the upper frame portion for adjusting the height of the seat relative to the lower frame portion between the normal operating height and a level above the normal operating height. Preferably, the upper frame portion is telescopically received in the lower frame portion. A locking mechanism can be provided for locking the upper and lower frame portions together at any number of seat heights.